public static List <LambdaExpression> Execute(LambdaExpression expression)
{
// Find projection for aggregates calculated over sequence
// specified by aggregatedSequence.
//
// Example:
// x => new {
// CountActive = x.Count(i => i.Active),
// SumActive = x.Sum(i => i.Active ? i.Value : 0),
// };
//
// The following expressions are returned:
//
// i => i.Active
// i => i.Acitve ? i.Value : 0
var finder = new AggregateProjectionFinder();
finder.aggregatedSequence = expression.Parameters.Count == 2
? expression.Parameters[1] // Result selector parameter in GroupBy
: expression.Parameters[0]; // Selector parameter in Select after GroupBy
finder.Visit(expression);
return(finder.result);
}
private MethodCallExpression VisitGroupBy(MethodCallExpression groupByCall, LambdaExpression selectProjection)
{
var groupBy = QueryParser.ParseGroupBy(groupByCall);
var projection = groupBy.ResultSelector ?? selectProjection;
if (projection != null)
{
var referenceFieldAccessors = AggregateProjectionFinder.Execute(projection)
.Select(ReferenceFieldAccessExtractor.Execute)
.Where(item => item != null)
.ToList();
if (referenceFieldAccessors.Count > 0)
{
groupBy.Source = Visit(groupBy.Source);
if (groupBy.ElementSelector != null)
{
AddGroupByItemWrapper(groupBy, referenceFieldAccessors);
}
groupBy.Source = referenceFieldAccessors.Aggregate(groupBy.Source, AddProjectionPrefetch);
return(QueryFactory.GroupBy(groupBy));
}
}
return(groupByCall);
}
